This makes 0 sense to me! Heater hose route

[AuroraGirl]

I was looking at this thinking it might be correct

no thats insane your limiting your original coolant flow and frankly im not sure that it would make your heater core that effective lol

 

[RaisedK5]

I see it now. I thought it was an either or diagram. Autos going to the rad and manual s going to the water pump

It IS an either or.

On non auto vehicles it went manifold (hot side) to core, core to water pump (cold side)

On auto vehicles it goes manifold to core, core to radiator, it does this to dump a little heat into the cold tank of the radiator where the trans cooler is to get the trans up to temp in cold weather.

I have never seen a factory tee in the return line.

 

[sidschev]

I was looking at this thinking it might be correct

this is correct ....

 

[75gmck25]

That setup in the last picture is how my ‘75 350 with TH350 is plumbed.

Mine also has HD cooling (standard when you order A/C), so it uses a longer PS belt that goes around the both the crankshaft and water pump (dual groove pulley on water pump). If the alternator belt breaks, the PS belt will still drive the water pump.

 

[mtbadbob]

It IS an either or.

On non auto vehicles it went manifold (hot side) to core, core to water pump (cold side)

On auto vehicles it goes manifold to core, core to radiator, it does this to dump a little heat into the cold tank of the radiator where the trans cooler is to get the trans up to temp in cold weather.

I have never seen a factory tee in the return line.

That's EXACTLY what my '87 auto does, nothing off the water pump. My manifold fitting is behind the TB though, but I'm pretty sure that's original. Not t's or y's in my system whatsoever.

 

[mtbadbob]

On my '87 auto, the wp is plugged, no heater hose connects to it. I'm 99% sure it's factory.

 

[Grit dog]

It IS an either or.

On non auto vehicles it went manifold (hot side) to core, core to water pump (cold side)

On auto vehicles it goes manifold to core, core to radiator, it does this to dump a little heat into the cold tank of the radiator where the trans cooler is to get the trans up to temp in cold weather.

I have never seen a factory tee in the return line.

I thought I had an explanation, but it’s been a while. Only SB/BB GMs I’ve worked on in forever is the boat and now the 86 gmc.
So just replaced the heater core on the 86. And it was and still is, water pump to core and radiator to core. Which doesn’t match either of the scenarios you mentioned.
Heat gets hot and works great. So idk….

 

[jimmy78]

On my '87 auto, the wp is plugged, no heater hose connects to it. I'm 99% sure it's factory.

I’m planning on going water pump to heater core return to rad. Only reason is

I thought I had an explanation, but it’s been a while. Only SB/BB GMs I’ve worked on in forever is the boat and now the 86 gmc.
So just replaced the heater core on the 86. And it was and still is, water pump to core and radiator to core. Which doesn’t match either of the scenarios you mentioned.
Heat gets hot and works great. So idk….

That’s my my plan. I need the port on the intake for a temp sensor. That’s where the wire goes to already so that’s where the sensor is going.

 

[legopnuematic]

My 76 (350 w/ac) was setup with one hose from the intake and the other hose to the radiator. When I changed radiators the new one didn’t have provision for the return hose there, so I ran it to the water pump.

My 79 (350 w/o ac) was setup like that from the factory:

You must be registered for see images attach

 

[jimmy78]

My 76 (350 w/ac) was setup with one hose from the intake and the other hose to the radiator. When I changed radiators the new one didn’t have provision for the return hose there, so I ran it to the water pump.

My 79 (350 w/o ac) was setup like that from the factory:

You must be registered for see images attach

Is this a manual transmission? The 79?

 

[legopnuematic]

Is this a manual transmission? The 79?

Both automatics (TH350’s)

 

[SquareRoot]

My 76 (350 w/ac) was setup with one hose from the intake and the other hose to the radiator. When I changed radiators the new one didn’t have provision for the return hose there, so I ran it to the water pump.

My 79 (350 w/o ac) was setup like that from the factory:

You must be registered for see images attach

LOL "It ran when I parked it"

 

[RaisedK5]

I thought I had an explanation, but it’s been a while. Only SB/BB GMs I’ve worked on in forever is the boat and now the 86 gmc.
So just replaced the heater core on the 86. And it was and still is, water pump to core and radiator to core. Which doesn’t match either of the scenarios you mentioned.
Heat gets hot and works great. So idk….

Hey man no worries. The 86 manual shows the path I describe as well. Plenty of variation thru the years, though so idk either...but if you think about the coolant flow on a std rotation water pump. Coolant goes from passenger tank (cold) to water pump (cold) to engine, thru engine to intake manifold (hot) to drivers tank (hot) and then getes cooled and starts over. So if you're going from wp to core to radiator, it's theoretically all on the cold side of flow until the thermostat opens. It all ends up hot in the end but like I said plenty of variation over the years and if it works...it works. Nothing wrong if it works the way you want.

You must be registered for see images attach

 

[tsgs84]

Can someone shed some light on this monstrosity of a heater hose routing.

Rad to heater core with tee to intake manifold

Heater core to water pump

This seems janky to say the least.

My 84 came with this setup, water pump is plugged off. Somebody told me it was the HD cooling option which makes sense as my truck came from Nevada. Hope this is helpful.

 

[jimmy78]

Hey man no worries. The 86 manual shows the path I describe as well. Plenty of variation thru the years, though so idk either...but if you think about the coolant flow on a std rotation water pump. Coolant goes from passenger tank (cold) to water pump (cold) to engine, thru engine to intake manifold (hot) to drivers tank (hot) and then getes cooled and starts over. So if you're going from wp to core to radiator, it's theoretically all on the cold side of flow until the thermostat opens. It all ends up hot in the end but like I said plenty of variation over the years and if it works...it works. Nothing wrong if it works the way you want.

You must be registered for see images attach

This has been the thought of being on the cold side till the thermostat opens. But does the connection on the intake not get flow till the thermostat is open anyway ?